1. Technical Field
The present invention relates to an automatic locking system and an automatic locking method for automatically locking the doors of a vehicle.
2. Related Art
Recently, a lot of attention is focused on a so-called automatic locking system for vehicles, which automatically locks the entry-and-exit doors of a vehicle. As an example of this system, the system as described in JP-A-2007-146440 is known. In this system, communication is established with an electronic key in a predetermined communication area around the doors outside the vehicle cabin. In the communication, an ID code included in a signal transmitted from the electronic key is compared with an ID code that has been registered in advance. Further, if the result of the comparison changes from OK to NG (i.e. not OK) in the case where all of the entry-and-exit doors are closed, all of the entry-and-exit doors are locked (e.g., see Patent Document 1).
The system described in JP-A-2007-146440 may not be able to lock the entry-and-exit doors under the conditions where the driver carrying the electronic key leaves the vicinity of the vehicle, a vehicle occupant not carrying the electronic key stays in the vehicle cabin, and the vehicle occupant then gets out of the vehicle and closes an entry-and-exit door. This is because, if the electronic key is located somewhere away from the vicinity of the doors when the vehicle occupant closes the entry-and-exit door, the result of the comparison mentioned above will not change from OK to NG even when all of the entry-and-exit doors are closed.